1. Field of the Invention
The invention relates to the field of antenna. More specifically, a dual-band antenna operates at wireless local area network.
2. The Related Art
According to the progress of the communication technology, the key development is the transfer from wired to wireless communication. A plurality of different wireless communication bands may be used by devices such as laptops. For example, the standards for wireless local area network (LAN) include the IEEE 802.11a band and the IEEE 802.11b/g.
In recent years, Wireless Local Area Network (WLAN) mobile communication products under IEEE 802.11a/b/g standards, such as WLAN cards for computers are gaining popularity in wireless communication market. Wherein, IEEE 802.11b/g standard is suitable for working at 2.4 GHz frequency band covering 2.412 GHz to 2.462 GHz, while IEEE 802.11a standard is suitable for working at 5 GHz frequency band covering 4.9 GHz to 5.87 GHz. Many WLAN mobile communication products want to be used under both IEEE 802.11a and IEEE 802.11b/g standard.
The data rate of the IEEE 802.11a/g standard is 54 Mbps which is high enough to transmit various data such as image data, video data and audio data. If the laptop would have wireless communication function using IEEE 802.11a and IEEE 802.11b/g standards over 54 Mbps, the antennas is necessary for operating at 2.4 GHz and 5.2 GHz bands.
A conventional dual-band antenna is disclosed in U.S. Pat. No. 7,196,668. The dual band antenna has a first antenna, an antenna array and a wireless module, which is configured in the laptops. The antenna array has a plurality of second antennas and a plurality of connectors connected to the second antennas. The distance between two adjacent second antennas is identical. The first antenna and the second antennas respectively operate at 2.4 GHz band and 5.2 GHz band.
The dual band antenna has the large dimension according to the distance between two adjacent second antennas being identical. It is necessary to retain a large space in the laptops for configuring the dual-band antenna in the laptops. The process for configuring the dual-band antenna in the laptop is complex because the distance between two adjacent second antennas is identical.